Switched-mode power supply (SMPS) systems are widely used in various electronic devices ranging from automobiles to cellular phones. A large number of these SMPS systems are powered by rechargeable and non-rechargeable batteries such as Alkaline, Lithium ion and Nickel Metal Hydride (NiMH). SPMS systems are designed to control the output for different loading conditions and exhibit good load regulation. These switching regulators are also designed to efficiently handle input supply voltage variation for short and long durations of time and provide a constant output.
Various electronic applications require SMPS systems to handle a wide range of operating conditions. These operating conditions may include a transient load condition and a line (battery) condition, a temperature variation, and a power saving mode. A digital or analog controller is used to provide static and dynamic responses over these different operating conditions. A digital or analog controller regulates the output by closing the feedback around the system. Proportional-integral-derivative (PID) controllers are often used in SMPS to handle responses to any output changes. In a PID controller, the proportional term is the error between the desired output state and the actual output. The derivative term is the change of proportional term over time, and a non-zero value indicates a rapidly changing system condition. The integral term is the accumulation of the proportional errors, and this term drives the control system to its final and stable value.